(1) Field of the Invention
The invention relates to a gatherer stitcher having at least one stitching station for stitching sheets, the stitching station being mounted on a stitching carriage that can move in the longitudinal direction of a gatherer chain during the stitching operation and at least one ejector unit being provided after the stitching station in a transport direction (X) of the sheets in order to eject the sheets. More particularly the invention pertains to an acceleration and/or braking unit disposed between the stitching carriage and the ejector unit.
(2) Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
Gatherer stitchers are generally paper-processing machines with which a product, for example a brochure, is assembled from a plurality of folded sheets and is stitched. Printed folded sheets from stacks, lying on folded sheet feeders or standing on the spine, are supplied in separated form, opened and placed on a gatherer chain. The number of folded sheets to be stitched is gathered and aligned on the gatherer chain by means of drivers. The gatherer chain transports the gathered folded sheets to a stitching device, where these are stitched with wire staples by means of stitching heads. Optionally, perforation of the products may be provided. In order to trim the edge of the stitched products, what is known as a trimmer (3-cutter) is normally provided after the ejector, from which the end products are transported onward to a delivery.
In gatherer stitchers, two stitching principles can expediently be employed: stitching at a standstill or stitching on the moving product. In order to perform stitching on the moving product, the stitching device, comprising stitching carriage and bending-over device or stitching station, has to be moved together with the product to be stitched and has to be coordinated with the movement of the latter, at least for some time.
The gatherer stitcher is often driven by a central electric motor. In this case, the various subassemblies, such as the stitching apparatus, the gatherer chain, the folded sheet feeder, the ejector, the trimmer and possibly further components are driven by various gear mechanisms and a common shaft, what is known as a king shaft.
The gatherer chain has a comparatively high transport speed, so that up to several booklets are produced per second. Because of this high transport speed of the sheets or booklets, it is possible for markings or scratching/rubbing tracks on the booklets and/or for tilting of the booklets to occur as a result of the deflection of the direction of movement of the booklets by means of the ejector. This leads, inter alia, to damage or impairment to the quality of the booklets produced.
It is precisely because of the aforementioned high transport speeds that even short stoppages of the gatherer stitcher lead to a considerable reduction in the booklets produced, on account of the faults described above. Furthermore, a relatively high overrun or backup with booklets wedged or jammed in one another is produced relatively quickly and in general can be eliminated only with a considerably great effort on repair.